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Transverse engine orientation

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Transverse engine orientation

PostFri Jul 12, 2013 5:01 pm

I was chatting with another Hoon (Brenden, b3quattro) earlier about the cars I've owned, and when I brought up my former Volvo 850, I remembered something - the engine's in sideways, of course, but it's flipped around from how most transverse engines are installed. The 850's engine faced right (from the inside of the car, left when staring into the engine bay) - the exhaust manifold was on the back, in other words, rather than up front as it is in most other transverse-engined cars I've seen/worked on.

Was Volvo just being ornery, or is there some sort of inherent advantage to having it laid out one way or the other? Brenden mentioned that he thought some countries required the fuel rail to be adequately protected, or some such thing.

- Sam
('96 NG900)
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Re: Transverse engine orientation

PostFri Jul 12, 2013 11:56 pm

All assumptions, all the post;
The side the transmission is on would be related to the car's native drive-handedness. It's easier to put the brake booster/clutch master cyl. over the transmission, so the transmission would be on the same side as the driver is in the car's target market.
I used to think it was silly to have the exhaust come out the front of transverse engines, then it has to be routed down and under or around the engine. But, this allows the engine to be closer to the firewall, and it's not difficult to pipe the intake around the side so it can reach the back of the engine. Front-exhaust is easier to service?
So why put it on the back? Since it's Volvo, probably crash reasons.
850s use Volvo's modular engine, which appears to only be used transversely, so it's not like they'd already developed the engine for longitudinality and they had to attach it to the only transverse transmission they had available and that's the way around they had to go. Clearly that's not the case so there's no use even bringing up such a theory.
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Re: Transverse engine orientation

PostSat Jul 13, 2013 9:34 am

The 850 way lets you put a single cat closer to the engine. When 850 was being designed, Volvo wanted a car that was more fuel efficient and meet future emissions regs easily without much performance and cost impacts. They had also had the PRV fiasco, so anything to make the engine unique to offer resistance to just using some other engine was seen as positive by some. There was also a small improvement to engine output in this way and that good considering how heavy the 850 got. The first few model years, the intake was ported, that's how concerned Volvo was about any little bit.
Well, you know what they say, "The candle that burns exponentially more durably, burns several decades after it was lit and for a completely different reason." - BlackIce_GTS


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Re: Transverse engine orientation

PostSun Jul 14, 2013 7:50 pm

My 2000 Voyager's I4 has the exhaust manifold on the back, like every 2.0/2.4l Chrysler EDZ. Makes changing the O2 sensor hell, hence why I've been putting it off. Changing the air intake gaskets couldn't be easier, though.

I'm fairly sure it has to do with warming the cat up quicker to improve cold engine NOx emissions, without having to use a pre-cat or air injection. Nissan tried the pre-cat route, but they have a nasty tendency of breaking down internally and destroying the engine, since ceramics are a great abrasive when combined with engine oil. Chrysler is also incredibly cheap, hence why the NS platform my van is based on lasted in some form up until 2009.

My friend is looking at an engine replacement or hardcore rebuild in his 2004 Sentra SE-R thanks to pre-cat initiated cylinder scoring.
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Re: Transverse engine orientation

PostThu Jul 18, 2013 10:34 am

There needs to be some clarification here. I'm going to call the side of the engine where the pulleys are the "front," the side where the transaxle mounts the "rear," with "left" and "right" defined accordingly.

The most common transverse inline engine design is to have the engine front on the right side of the vehicle, with exhaust on the engine's left side.

A second, but very common, design is to have the engine front on vehicle right, with exhaust on the engine right.

A third design, seen on Hondas and old British Minis, has the engine front facing vehicle left. This is what BlackIce_GTS was getting at--these powertrains were initially developed for RHD countries. In Hondas, the exhaust is on the engine right. In the British cars, the exhaust is on the engine left.

Hence we have all four permutations, and all four have been made in large numbers.

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